Re: [PATCH v5 5/7] powerpc/pseries: flush SLB contents on SLB MCE errors.
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2018-07-02 22:08:58
On Mon, 02 Jul 2018 11:17:06 +0530 Mahesh J Salgaonkar [off-list ref] wrote:
From: Mahesh Salgaonkar <redacted> On pseries, as of today system crashes if we get a machine check exceptions due to SLB errors. These are soft errors and can be fixed by flushing the SLBs so the kernel can continue to function instead of system crash. We do this in real mode before turning on MMU. Otherwise we would run into nested machine checks. This patch now fetches the rtas error log in real mode and flushes the SLBs on SLB errors. Signed-off-by: Mahesh Salgaonkar <redacted> --- arch/powerpc/include/asm/book3s/64/mmu-hash.h | 1 arch/powerpc/include/asm/machdep.h | 1 arch/powerpc/kernel/exceptions-64s.S | 42 +++++++++++++++++++++ arch/powerpc/kernel/mce.c | 16 +++++++- arch/powerpc/mm/slb.c | 6 +++ arch/powerpc/platforms/powernv/opal.c | 1 arch/powerpc/platforms/pseries/pseries.h | 1 arch/powerpc/platforms/pseries/ras.c | 51 +++++++++++++++++++++++++ arch/powerpc/platforms/pseries/setup.c | 1 9 files changed, 116 insertions(+), 4 deletions(-)
+TRAMP_REAL_BEGIN(machine_check_pSeries_early) +BEGIN_FTR_SECTION + EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200) + mr r10,r1 /* Save r1 */ + ld r1,PACAMCEMERGSP(r13) /* Use MC emergency stack */ + subi r1,r1,INT_FRAME_SIZE /* alloc stack frame */ + mfspr r11,SPRN_SRR0 /* Save SRR0 */ + mfspr r12,SPRN_SRR1 /* Save SRR1 */ + EXCEPTION_PROLOG_COMMON_1() + EXCEPTION_PROLOG_COMMON_2(PACA_EXMC) + EXCEPTION_PROLOG_COMMON_3(0x200) + addi r3,r1,STACK_FRAME_OVERHEAD + BRANCH_LINK_TO_FAR(machine_check_early) /* Function call ABI */
Is there any reason you can't use the existing machine_check_powernv_early code to do all this?
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diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c index efdd16a79075..221271c96a57 100644 --- a/arch/powerpc/kernel/mce.c +++ b/arch/powerpc/kernel/mce.c@@ -488,9 +488,21 @@ long machine_check_early(struct pt_regs *regs) { long handled = 0; - __this_cpu_inc(irq_stat.mce_exceptions); + /* + * For pSeries we count mce when we go into virtual mode machine + * check handler. Hence skip it. Also, We can't access per cpu + * variables in real mode for LPAR. + */ + if (early_cpu_has_feature(CPU_FTR_HVMODE)) + __this_cpu_inc(irq_stat.mce_exceptions); - if (cur_cpu_spec && cur_cpu_spec->machine_check_early) + /* + * See if platform is capable of handling machine check. + * Otherwise fallthrough and allow CPU to handle this machine check. + */ + if (ppc_md.machine_check_early) + handled = ppc_md.machine_check_early(regs); + else if (cur_cpu_spec && cur_cpu_spec->machine_check_early) handled = cur_cpu_spec->machine_check_early(regs);
Would be good to add a powernv ppc_md handler which does the cur_cpu_spec->machine_check_early() call now that other platforms are calling this code. Because those aren't valid as a fallback call, but specific to powernv.
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diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c index 48fbb41af5d1..ed548d40a9e1 100644 --- a/arch/powerpc/platforms/powernv/opal.c +++ b/arch/powerpc/platforms/powernv/opal.c@@ -417,7 +417,6 @@ static int opal_recover_mce(struct pt_regs *regs, if (!(regs->msr & MSR_RI)) { /* If MSR_RI isn't set, we cannot recover */ - pr_err("Machine check interrupt unrecoverable: MSR(RI=0)\n");
What's the reason for this change?
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recovered = 0; } else if (evt->disposition == MCE_DISPOSITION_RECOVERED) { /* Platform corrected itself */diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h index 60db2ee511fb..3611db5dd583 100644 --- a/arch/powerpc/platforms/pseries/pseries.h +++ b/arch/powerpc/platforms/pseries/pseries.h@@ -24,6 +24,7 @@ struct pt_regs; extern int pSeries_system_reset_exception(struct pt_regs *regs); extern int pSeries_machine_check_exception(struct pt_regs *regs); +extern int pSeries_machine_check_realmode(struct pt_regs *regs); #ifdef CONFIG_SMP extern void smp_init_pseries(void);diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c index 851ce326874a..9aa7885e0148 100644 --- a/arch/powerpc/platforms/pseries/ras.c +++ b/arch/powerpc/platforms/pseries/ras.c@@ -427,6 +427,35 @@ int pSeries_system_reset_exception(struct pt_regs *regs) return 0; /* need to perform reset */ } +static int mce_handle_error(struct rtas_error_log *errp) +{ + struct pseries_errorlog *pseries_log; + struct pseries_mc_errorlog *mce_log; + int disposition = rtas_error_disposition(errp); + uint8_t error_type; + + if (!rtas_error_extended(errp)) + goto out; + + pseries_log = get_pseries_errorlog(errp, PSERIES_ELOG_SECT_ID_MCE); + if (pseries_log == NULL) + goto out; + + mce_log = (struct pseries_mc_errorlog *)pseries_log->data; + error_type = rtas_mc_error_type(mce_log); + + if ((disposition == RTAS_DISP_NOT_RECOVERED) && + (error_type == PSERIES_MC_ERROR_TYPE_SLB)) { + /* Store the old slb content someplace. */ + slb_flush_and_rebolt_realmode(); + disposition = RTAS_DISP_FULLY_RECOVERED; + rtas_set_disposition_recovered(errp); + } + +out: + return disposition; +} + /* * Process MCE rtas errlog event. */@@ -503,11 +532,31 @@ int pSeries_machine_check_exception(struct pt_regs *regs) struct rtas_error_log *errp; if (fwnmi_active) { - errp = fwnmi_get_errinfo(regs); fwnmi_release_errinfo();
Should the fwnmi_release_errinfo be done in the realmode path as well now, or is there some reason to leave it here?
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+ errp = fwnmi_get_errlog(); if (errp && recover_mce(regs, errp)) return 1; } return 0; } + +int pSeries_machine_check_realmode(struct pt_regs *regs) +{ + struct rtas_error_log *errp; + int disposition; + + if (fwnmi_active) { + errp = fwnmi_get_errinfo(regs); + /* + * Call to fwnmi_release_errinfo() in real mode causes kernel + * to panic. Hence we will call it as soon as we go into + * virtual mode. + */ + disposition = mce_handle_error(errp); + if (disposition == RTAS_DISP_FULLY_RECOVERED) + return 1; + } + + return 0; +}diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index 60a067a6e743..249b02bc5c41 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c@@ -999,6 +999,7 @@ define_machine(pseries) { .calibrate_decr = generic_calibrate_decr, .progress = rtas_progress, .system_reset_exception = pSeries_system_reset_exception, + .machine_check_early = pSeries_machine_check_realmode, .machine_check_exception = pSeries_machine_check_exception, #ifdef CONFIG_KEXEC_CORE .machine_kexec = pSeries_machine_kexec,